A heart rate can be measured using various mechanisms, including electrocardiogram (ECG) and photoplethysmogram (PPG). ECG sensors use electrical activity of a heart to measure the heart rate. PPG sensors use an optical technology to measure the rate of blood flow and derive the heart rate.
A person's heart rate can be measured using ECG or PPG while the person performs an exercise. The person can exercise at various intensity levels. Generally, the higher the intensity level, the higher the heart rate becomes. The person can benefit by knowing the intensity level at which the person exercises. Accordingly, it is desirable to provide methods and systems of determining the intensity level for a person performing an exercise.